The present invention generally relates to the sensing of electrical potentials in tissue and to the radio frequency (RF) ablation of tissue, and in particular to probes for doing so and methods of constructing such probes.
It is known that damaged heart muscles can cause abnormal activities of the electrical signals that are generated to create muscle contraction. As a result of this damaged tissue, the heart instead of beating as "normal" can have an increased heartbeat (ventricular tachycardia).
Hitherto, such cardiac defects have been treated either by means of drugs or by means of a catheter inserted into the heart via a patient's blood passages (e.g., a vein). With drug treatment, the effects are not entirely predictable and often many side effects occur. In general, the treatment with drugs is thought to be only approximately 30 to 35% successful.
The second treatment involves the insertion of electrodes into the heart via a catheter inserted through a vein. Such a catheter is typically an elongated, cylindrical body made of flexible material that is fitted with two or more electrodes at a distal end. Radio frequency energy is then applied between two electrodes so as to cause ablation. In particular, it is desired, in this way, to remove the defective tissue, or at least change its electrical properties, to prevent re-entry of the electrical signals necessary to cause contraction of the muscle. It has been found difficult to locate correctly the catheter and the necessary electrodes with any precision, partly due to the interior nature of the mechanism of the arrhythmia and also due to the continuous movement of the heart muscles.